1. Field of the Invention
The present invention relates to a camera system including an optical unit equipped with an image-taking optical system which forms subject light into an image, and a camera body to which the optical unit is detachably attached.
2. Description of the Related Art
There has been heretofore known a digital camera with interchangeable lenses, a camera system of which is configured of an interchangeable lens unit with a built-in taking lens, and a camera body with a built-in image pickup device, having the lens unit attached thereto. The digital camera with interchangeable lenses has an advantage of permitting users to select a lens unit suitable for use from among the lens units according to what purpose the users do shooting for.
Recently, the digital camera with interchangeable lenses has undergone evolutionary development into a digital camera with interchangeable heads, in which a lens unit with an image pickup device, which has a taking lens and an image pickup device built-in, is attached to a camera body (the lens unit with image pickup device will be hereinafter referred to simply as a “camera head”). In the digital camera with interchangeable heads, an image signal is formed by shooting in the camera head, and then, is transferred to the camera body. Furthermore, among these digital cameras with interchangeable heads, there is another type of a digital camera with interchangeable heads, which is contrived to prevent a slowdown in processing speed due to centralized control. In this type of camera, functions required for control of the digital camera are assigned to a camera head and a camera body, which are provided with respective control units to perform the respective assigned functions (see, e.g., Japanese Patent Application Laid-open No. 2000-50130). For example, the function assignment can be made so that the camera head forms RAW image data by analog to digital conversion of an image signal, and that the camera body converts the image data in a recording format by JPEG (Joint Photographic Experts Group) compression or the like.
However, the digital camera with interchangeable heads, as mentioned above, is often designed to permit users to select among various shooting modes, such as moving picture shooting mode and continuous shooting mode, in addition to normal still picture shooting mode. The camera system capable of selecting the shooting mode may require too long a time to transfer image data, if in a form of RAW data, from the camera head to the camera body, thus causing a delay in the transfer. Moreover, the camera head may be unable to withstand heat produced incident to power consumption required for the camera head to convert a data format of the image data into a recording format. It is therefore desired to make the assignment of appropriate functions to the camera head and the camera body.